Examine source code of Joker

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Joker",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/0.jpg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "center top"
      ],
      "additional_backgrounds_tiling": [
        "repeat-x"
      ]
    },
    "colors": {
      "toolbar": "rgb(69, 90, 102)",
      "toolbar_text": "rgb(39, 6, 10)",
      "frame": "rgb(7, 12, 16)",
      "tab_background_text": "rgb(220, 168, 175)",
      "toolbar_field": "rgb(91, 54, 59)",
      "toolbar_field_text": "rgb(123, 127, 204)",
      "tab_line": "rgb(102, 49, 59)",
      "popup": "rgb(38, 38, 144)",
      "popup_text": "rgb(33, 33, 156)",
      "ntp_background": "rgb(38, 38, 144)",
      "ntp_text": "rgb(38, 38, 144)",
      "sidebar_border": "rgb(74, 74, 97)",
      "sidebar_highlight_text": "rgb(13, 13, 38)",
      "toolbar_bottom_separator": "rgb(70, 70, 131)",
      "tab_loading": "rgb(102, 49, 59)"
    }
  }
}